We propose that return flowering of `Fuji' apple can be improved if sufficient flower clusters are removed during or shortly after bloom. In this study conducted at Corvallis, Ore., we evaluated two synthetic auxins, MCPB-ethyl and the Na salt of NAA, each at 0, 4, 8 and 16 ppm, as blossom cluster thinners. Each auxin treatment was applied alone or with 100 ppm ethephon as a tank mix. Six-year-old `Fuji'/M.26 trees were sprayed at full bloom of the king flowers (≈85% of whole-tree full bloom). A follow-up treatment of Sevin XLR (800 ppm carbaryl) was made at 11-mm fruit diameter to determine if carbaryl's known effectiveness as a fruitlet thinner was influenced by the bloom-time auxin or auxin + ethephon treatments. MCPB-ethyl proved ineffective as a bloom-time thinner, whereas the NAA effect on cluster removal was linear with concentration, 16 ppm NAA completely defruiting 33% of initial flower clusters. On control trees fewer than 12% of flowering clusters failed to set fruit. Ethephon alone defruited 25% of the clusters and NAA+ethephon defruited 51% of clusters. It is notable that the NAA and ethephon + NAA treatments did not reduce fruit set on the remaining clusters, resulting in considerable need for hand-thinning. Carbaryl effectively reduced total crop load by increasing the number of defruited clusters and reducing the incidence of doubles and triples. There was evidence to suggest that its effectiveness was compromised by the bloom-time NAA and/or ethephon sprays.
Abstract
Newly budded trees of ‘Valencia’ orange [Citrus sinensis (L.) Osbeck] on rough lemon (C. jambhiri Lush.), alemow (C. macrophylla Wester), Troyer citrange (Poncirus trifoliata Raf. ⨯ C. sinensis), and P. trifoliata were sprayed with 2 concentrations of naphthaleneacetic acid (NAA) to inhibit rootstock sprouting, buds being protected with budding tape. Good control of rootstock sprouts was obtained on rough lemon and P. trifoliata but translocated NAA inhibited scion bud initiation. There was partial suppression of rootstock sprouts on Troyer citrange but no scion bud inhibition. NAA did not control rootstock sprouts on alemow.
Abstract
Emerging primocanes of red raspberry, Rubus ideaus L. ‘Boyne’, were sprayed with naphthaleneacetic acid (NAA) at concentrations of 0.5, 1.0, and 1.5% when shoots were 7–13-cm-tall or at 1.0 and 2.0% when they were 13–20-cm-tall. Treated primocanes exhibited leaf cupping and epinasty followed by withering and death. Untreated floricanes and primocanes emerging after treatment were normal. Treatment with NAA at all rates restricted the height of primocanes emerging after treatment. Fruit yield the year following was reduced by NAA applied to shoots 13-20-cm-tall.
The effect of temperature on uptake of C-labeled NAA was determined using detached apple leaves. Uptake by both adaxial and abaxial surfaces was measured at 15 and 35C over a 24-hotm period. Foliar absorption of NAA by the abaxial surface was greater than that by the adaxial surface. Absorption by the abaxial surface increased linearly (P < 0.001) with temperature over the range of 15 to 35C. These results are discussed in relation to fruit thinning. Chemical name used: 2-(1-naphthyl)acetic acid (NAA).
Abstract
Treatments with gibberellic acid (GA3), naphthaleneacetic acid (NAA), or their combination to Cyclamen persicum Mill. ‘Swan Lake’ plants resulted in separate, antagonistic, or cooperative effects on leaf lamina unfolding, days to flowering, number of leaves at first flower, and length of the first flower's peduncle. Generally, GA3 accelerated plant growth nonspeciflcally, resulting in plants which flowered earlier than untreated plants, but with a similar number of leaves at first bud flowering. The combination of GA3 plus NAA specifically accelerated flowering, but this effect diminished as the treatment frequency or quantity of the NAA application increased.
Abstract
Leaf explants from ‘Sugar Daddy’ and ‘Sugar Plum’ petunia (Petunia hybrida L.) were pretreated in solutions of 0, 200, 400, and 800 mg/liter 6-benzylamino purine (BA) and were placed in a cytokinin-free modified Murashige and Skoog (MS) medium, to which 0.05, 0.1, or 0.2 mg/liter naphthaleneacetic acid (NAA) were incorporated to test interaction. NAA at 0.05 or 0.1 mg/liter increased shoot number, fresh weight, and shoot quality rating for ‘Sugar Daddy’, while in ‘Sugar Plum’ addition of NAA increased shoot fresh weight and improved shoot quality rating without any effect on shoot number.
Abstract
Leaves from succinic acid-2,2-dimethylhydrazide (daminozide)-treated seedlings of ‘McIntosh’ apple (Malus domestica Borkh) accumulated significantly more 45Ca than those from 1-napthaleneacetic acid (NAA)-treated seedlings. Stem sections from daminozide-treated seedlings accumulated significantly more 45Ca than stems from control seedlings. Total 45Ca content in daminozide-treated seedlings was significantly greater than in either controls or NAA-treated seedlings. The expected reduction in total shoot length by treatment with daminozide, NAA + daminozide and NAA was noted. The increases in 45Ca content in all treatments appear to be due in part to the concentration effect of reduced shoot growth and in part to an effect of daminozide on rate of uptake.
These studies with apple (Malus domestica Borkh.) spur tissues were conducted to investigate the mechanism whereby NAA may stimulate fruit abscission in the spring but acts to prevent fruit drop in the fall. NAA-induced ethylene evolution from `Delicious' spurs in vivo was similar to that evolved from excised leaf and fruit tissues that later were treated in the laboratory and incubated in darkness at 20C. The peak in ethylene production occurred 24 hours after treatment at 30C, 48 hours after treatment at 20C, and production was still increasing 72 hours after treatment at 10C. Leaf tissue showed the greatest induction of ethylene from NAA followed by fruit and petiolar tissues. Induction was greatest early in the season and declined steadily until about “June drop.” After this time, none of the tissues showed significant capacity for ethylene induction. Chemical names used: 2-(1 -naphthyl) acetic acid (NAA).
Foliar sprays of TIBA inhibited the growth of apple seedlings, and induced bitter pit of field grown `Golden Delicious' fruit. Total Ca levels were significantly decreased in the stems and leaves of apple seedlings, and in fruit peel. Foliar sprays of NAA increased total Ca content in shoots of apple seedlings. The Ca levels in the roots of seedlings were affected less by TIBA and/or NAA sprays than that of shoots. Irrigation after TIBA treatment inhibited apple seedling growth, and decreased total Ca content in shoots and roots, while NAA increased the growth and Ca content in the seedlings. TIBA via lanolin mixture to the shoot inhibited growth, and decreased the Ca content in shoots and roots of apple seedlings. NAA via lanolin mixture did not affect growth, whereas it increased the Ca content in the shoots of apple seedlings.
Abstract
Naphthaleneacetic acid (NAA) applied as a spray to apple trees on May 7 reduced fruit set, number of seed per fruit, percent and amount of reducing sugar in flesh of young fruits but did not affect protein level or fruit size. Fruit from trees sprayed with NAA on May 18 had more seed and less reducing sugar than the checks. The late NAA spray also reduced fruit size and set but did not affect the protein level of flesh or seed. Sprays of 1-naphthyl methylcarbamate (Sevin) applied on the same dates reduced fruit set but did not affect other factors measured. We propose that the reduced metabolite supply (reducing sugar) in the young fruit is the primary reason for reduced fruit set on trees sprayed with NAA and that effect on seed number is not related to this change in composition.